As of June 30, 1970, federal regulations required the operator of each underground coal mine to maintain the average concentration of respirable dust below legislative standards. As of March 1, 1971, over 152,000 respirable dust samples have been processed by the Bureau of Mines. Approximately 75 percent of underground working sections are being sampled in accordance with federal regulations. Results indicate that 72 percent of the sections which have completed at least one basic sampling cycle are below 3.0 Mg/m3, the standard in effect under the Federal Coal Mine Health and Safety Act of 1969 (Public Law 91-173). Notices of violation were issued on 1,670 underground mines for failure to begin a sampling program; withdrawal orders were issued in 64 of these instances. Notices of violation were issued on 1,121 sections where applicable dust levels were exceeded; withdrawal orders were issued in seven of these instances. There are 381 mining sections currently operating on permits from the interim compliance panel.